We present new developments in jet reconstruction and calibration for LHC Run3. A new regression approach for jet calibration is explored and pileup mitigation techniques are developed for joint reconstruction of hadronic taus and jets.
A fundamental aspect of CMS researches concerns the identification and characterisation of jets originating from quarks and gluons produced in high-energy proton-proton collisions. Electroweak scale resonances (Z/W bosons), Higgs bosons and top quarks are often produced with high Lorentz-boosts, where their products become highly collimated large and massive jets, usually reconstructed as AK8...
Flavour-tagging is a critical component of the ATLAS experiment physics programme. Existing flavour tagging algorithms rely on several low-level taggers, which are a combination of physically informed algorithms and machine learning models. A novel approach presented here instead uses a single machine learning model based on reconstructed tracks, avoiding the need for low-level taggers based...
New searches with exotic jet substructure techniques from CMS are presented. Signatures with challenging reconstruction techniques include displaced jets, closely merge photon-pairs and soft unclustered energy patterns. New reconstruction techniques making use of machine learning and physics results are presented.
Multi-head attention based Transformers have taken the world by storm, given their outstanding capacity of learning accurate representations of diverse types of data. Famous examples include Large Language Models, such as ChatGPT, and Vision Transformers, like BEiT, for image generation. In this talk, we take these major technological advancements to the realm of jet physics. By creating a...
The Lund jet plane (LJP) is an observable introduced to better understand the radiation pattern of jets in terms of the jets-within-the-jets found with iterative Cambridge/Aachen declustering. The LJP is a two-dimensional representation of the phase space of $1\to 2$ branchings, where the logarithm of the relative transverse momentum ($k_t$) and the logarithm of the rapidity-azimuth distance...
Parton showers are immensely flexible tools that are currently undergoing significant development in terms of their logarithmic accuracy, first to next-to-leading logarithmic (NLL) and more recently towards next-to-NLL (NNLL) accuracy. These improvements should make them significantly more powerful tools for precision collider physics, including jet substructure studies. I will present recent...
In this talk, we introduce energy-weighted observable correlations (EWOCs): generalizations of the energy-energy correlator (EEC) which use subjets to characterize a wide variety of correlations between collective degrees of freedom in high-energy particle collisions. EWOCs use subjets to produce a manifestly infrared and collinear safe extension of the EEC, which probes energy-weighted...
Fragmentation of heavy quarks into heavy-flavoured hadrons receives both perturbative and non-perturbative contributions. We consider perturbative QCD corrections to heavy quark production in $e^+e^-$ collisions to next-to-next-to-leading order accuracy in QCD with next-to-next-to-leading-logarithmic resummation of quasi-collinear and soft emissions.
We study multiple matching schemes, and...
We report progress on the Heavy-Flavor Non-Relativistic Evolution (HF-NRevo) setup, a novel methodology to address the quarkonium formation within the fragmentation approximation. Our analysis addresses the moderate to large transverse-momentum regime, where the production mechanism based on the leading-twist collinear fragmentation from a single parton is expected to prevail over the...
We present a study on single heavy baryons' spectra and strong decay widths. The masses of single heavy baryons up to the D-wave are calculated within a constituent quark model, employing the three-quark and quark-diquark schemes. In this contribution, we discuss the possible assignment of the recently discovered $\Omega_c^0(3327)$, $\Lambda_b(6146)^0$, $\Lambda_b(6152)^0$, $\Xi_b(6327)^{0}$,...
We present the first theoretical calculation of nonfactorizable charm-quark loop contributions to the $B_s\to \gamma\, l^+l^-$ amplitude. This contribution involves the $B$-meson three-particle Bethe-Salpeter amplitude, $\langle 0|\bar s(y)G_{\mu\nu}(x)b(0)|\bar B_s(p)\rangle$, for which we take into account constraints from analyticity and continuity. We calculate the relevant form factors,...
Most research in high-energy physics nowadays begins with data. In recent years, effectively managing an increasing volume of data has become crucial for most publications. This holds true not only for high-energy physics but also for a wide range of activities, including healthcare, economics, computing, and business.
Traditionally, researchers analyze data by writing extensive code in...
The precise measurement of the jet energy and mass scales are a crucial input to many physics measurements that use the proton-proton collision data recorded by the ATLAS detector at the LHC. The energy determination of quark jets, which originate from bottom quarks, is challenging as, for example, these types of jets can contain leptonic heavy-flavour decays into a charged lepton and an...
We present a generic approach that deals with jet constituents to derive the jet energy scale (JES) uncertainty. It uses single-particle E/p response measurements obtained from 13 TeV Run 2 LHC data from proton-proton collisions. The E/p method offers a higher level of precision compared to the traditional pT-balance method, but, is in good agreement with it. Both methods are combined to...
This research discusses topics in the field of Quantum CromoDynamics and high energy physics. We consider an electron-positron scattering process and introduce a so-called superinclusive observable, suggested to us by Giorgio Parisi. This observable allows one to study the energy flow of an event due to QCD final-state radiation. The aim of the research is to give a theoretical prediction of...
The identification of top quark decays, known as top tagging, is a crucial component in many measurements and searches at the Large Hadron Collider (LHC). Recently machine learning techniques have greatly improved the performance of top tagging algorithms. This poster presents the performance of several machine learning based jet tagging methods. In particular the performance of a Lund jet...
This poster presents the reconstruction of missing transverse momentum (pTmiss) in proton-proton collisions, in Run-2 and Run-3 data-taking at the ATLAS experiment. This is a challenging task involving many detector inputs, combining fully calibrated electrons, muons, photons, hadronically decaying τ-leptons, hadronic jets, and soft activity from remaining tracks. Several pTmiss 'working...
Identifying boosted hadronic top quarks is a major challenge in the CMS physics program, both in Standard Model measurements and searches for new phenomena. Many excellent tools are available to identify wide-angle jets with top quark flavor. However, the intermediate regime between resolved and highly boosted jets is poorly covered. In recent years, CMS has introduced HOTVR, a variable...
Pileup, or the presence of multiple independent proton-proton collisions within the same bunch-crossing, has been critical to the success of the LHC, allowing for the production of enormous proton-proton collision datasets. However, the typical LHC physics analysis only considers a single proton-proton collision in each bunch crossing; the remaining pileup collisions are viewed as an...
In this talk, we discuss hadronic jets that are tagged as heavy-flavoured, i.e. they contain either beauty or charm. In particular, we consider heavy-flavour jets that have been groomed with the Soft Drop algorithm. In order to achieve a deeper understanding of these objects, we apply resummed perturbation theory to jets initiated by a massive quark and we
perform analytic calculations for...
In this talk I will present our research activity on jets substructure with heavy flavour. Our primary goal is to obtain a more profound understanding of these objects. To this end, we employ resumed perturbation theory tailored specifically for jets initiated by heavy quarks. Furthermore, we will present analytical calculations targeting various observables that characterise jets, including...
Understanding the behaviour of heavy quarks is important for painting a coherent picture of QCD, both formally and phenomenologically, and the upcoming runs at the LHC will provide unprecedented statistics for precision measurements related to heavy flavor. A natural object for initiating these studies are Energy Correlators, which measure correlations of energy flow at collider experiments....
The development of iterative declustering techniques has brought the ability to reconstruct the jet tree and access the building blocks of the QCD parton shower. The iterative declustering of an angular-ordered jet allows to access the kinematic properties and mass effects at the level of each individual emission. In order to expose mass effects in heavy flavor-tagged jets, we study the...
Several physics scenarios beyond the Standard Model predict the existence of new particles that can subsequently decay into a pair of Higgs bosons. These include pairs of SM-like Higgs bosons (HH) as well as asymmetric decays into two scalars of different masses (SH). For sufficiently high masses, the scalar S and the Higgs boson are Lorentz-boosted, thus the decay products are produced...
Search channels including at least one Higgs boson plus another particle have formed an important part of the program of new physics searches. In this talk, the status of these searches by the CMS Collaboration is reviewed. Searches are discussed for resonances decaying to two Higgs bosons, a Higgs and a vector boson, or a Higgs boson and another new resonance, with proton-proton collision...
We present a phenomenology study probing the Supersymmetric Standard Model (SSM) at the Large Hadron Collider for a previously unexplored region of the parameter space.
In particular, we consider proton-proton collisions at $\sqrt{s}=13$ and $\sqrt{s}=14$ TeV and investigate the production of GeV-scale first and second-generation neutralinos $\widetilde{\chi}_{1}^{0}$ and...
We present results from recent searches for resonances with enhanced couplings to top quarks or W bosons, collected with the CMS detector at a center-of-mass energy of 13 TeV. The analyses presented rely on state-of-the-art boosted-object identification techniques to reconstruct hadronic and leptonic top quark and W boson decays, targeting various signatures from single and pair production of...
Various searches for new resonances using unsupervised machine learning for anomaly detection are presented. These searches look at two-body invariant masses including leptons, at a heavy resonance Y decaying into a Standard Model Higgs boson H and a new particle X in a fully hadronic final state, or at the masses of two jets.
A model-agnostic search for new physics in the dijet final state with the CMS experiment is presented. Other than the requirement of a narrow dijet resonance with a mass in the range of 1800-6000 GeV, minimal additional assumptions are placed on the signal hypothesis. Search regions are obtained by utilizing multivariate machine learning methods to select jets with anomalous substructure. A...
Approximately one-fourth of the energy density of the known Universe is attributed to Dark Matter (DM), the nature of which remains enigmatic. If DM is made of particles, producing and studying them at the Large Hadron Collider may be possible. A promising method to achieve it is to consider a monojet channel, in which at least one hard jet recoils against a missing transverse momentum, and...
We present DarkCLR, a novel framework for detecting semi-visible jets at the LHC. DarkCLR uses a self-supervised contrastive-learning approach to create observables that are approximately invariant under relevant transformations. We use background-enhanced data to create a sensitive representation and evaluate the representations using a normalized autoencoder as a density estimator. Our...
The search for heavy resonances beyond the Standard Model (BSM) is a key objective at the LHC. While the recent use of advanced deep neural networks for boosted-jet tagging significantly enhances the sensitivity of dedicated searches, it is limited to specific final states, leaving vast potential BSM phase space underexplored. In this talk, we introduce a novel experimental method,...
The likelihood-ratio test can be used to perform a goodness-of-fit test between a reference model and observations if the alternative hypothesis is selected from data by exploring a rich parametrised family of functions. The New Physics Learning Machine (NPLM) methodology has been developed as a concrete realisation of this idea, to perform model-independent searches at collider experiments....
The Energy Mover’s Distance (EMD) has seen use in collider physics as a metric between events and as a geometric method of defining infrared and collinear safe observables. Recently, the spectral Energy Mover’s Distance (SEMD) has been proposed as a more analytically tractable alternative to the EMD. In this work, we obtain a closed-form expression for the Riemannian-like p = 2 SEMD metric...
To control the scheme of the Monte-Carlo (MC) top quark mass parameter several ingredients are mandatory, concerning the knowledge of the IR dynamics of the top mass sensitive observable, the MC parton shower and the MC hadronization evolution. I discuss these ingredients and their interplay for the simple case of 2-jettiness for boosted top production in electron-positron annihilation, where...
In this contributions we will present new results that relate the top quark mass parameter in Monte Carlo generators with a field-theoretical mass scheme. In our study, Pythia8 predictions for the groomed top jet mass distribution in pp -> ttbar production are compared with first-principle calculations at NNLL accuracy. The formal accuracy is improved (from NLL to NNLL) with respect to...
Unfolded data can be used to measure the top mass, but also to search for unexpected kinematic correlations in top decay events. We show how generative unfolding can be used for both tasks and how the results benefit from the unbinned, high-dimensional unfolding. Our method includes an unbiasing step with respect to the top mass used during training data and promises significant advantages...
In the past decade, there have been significant developments in jet measurements. Initially, the emphasis was primarily on measuring the jet production cross-sections in vacuum and their modification in the Quark-Gluon Plasma (QGP) medium. The current investigations have shifted towards probing jet substructure, aiming to understand the intricate interplay of the perturbative and the...
Measuring jet substructure in heavy-ion collisions provides an opportunity to study detailed aspects of the dynamics of jet quenching in the hot and dense QCD medium created in these collisions. This talk presents a set of complementary ATLAS measurements of jet suppression and substructure performed using various jet definitions, constituents, and grooming techniques in Pb+Pb collisions....
search for medium-induced jet transverse momentum broadening is performed with isolated photon-tagged jet events in proton-proton (pp) and lead-lead (PbPb) collisions at nucleon-nucleon center-of-mass energy $5.02\TeV$. The difference between jet axes as determined via energy-weight and winner-take-all clustering schemes, also known as the decorrelation of jet axes and denoted $\Delta j$, is...
This talk presents the first measurements of the groomed jet radius $R_{\mathrm{g}}$ and the jet girth $g$ in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables $R_{\mathrm{g}}$ and $g$ provide a quantitative measure of how narrow or broad a jet is. The...
The modifications imprinted on jets due to their interaction with QGP are assessed by comparing samples of jets produced in AA collisions and pp collisions. The standard procedure for doing so, however, ignores the effect of bin migration, i.e, it compares specific observables for jet populations at the same reconstructed jet transverse momentum ($p_T$). Since jet $p_T$ is itself modified by...
Energy correlators, which as a jet-substructure observable measure correlations between energy detectors (calorimeters) in a collider experiment, have received significant attention over the last few years in both the theory/phenomenology and experimental communities. This success has prompted investigations into how energy correlators can be further used, such as in the study of both hot and...
We propose a new approach to learning powerful jet representations directly from unlabelled data. The method employs a Particle Transformer to predict masked particle representations in a latent space, overcoming the need for discrete tokenization and enabling it to extend to arbitrary input features beyond the Lorentz four-vectors. We demonstrate the effectiveness and flexibility of this...
How can one fully harness the power of physics encoded in relativistic $N$-body phase space? Topologically, phase space is isomorphic to the product space of a simplex and a hypersphere and can be equipped with explicit coordinates and a Riemannian metric. This natural structure that scaffolds the space on which all collider physics events live opens up new directions for machine learning...
